Dresden 2006 – wissenschaftliches Programm
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O: Oberflächenphysik
O 29: Poster session II (Nanostructures, Magnetism, Particles and clusters, Scanning probe techniques, Time-resolved spectroscopy, Structure and dynamics, Semiconductor surfaces and interfaces, Oxides and insulators, Solid-liquid interfaces)
O 29.18: Poster
Mittwoch, 29. März 2006, 14:30–17:30, P2
Monte Carlo simulations of small transition metal oxide clusters: a comparison of numerical efficiency — •Ralf Gehrke and Karsten Reuter — Fritz-Haber-Institut, Faradayweg 4-6, D-14195 Berlin, Germany
Structural information is a key prerequisite to understand the peculiar chemical, optical, magnetic and materials properties of small transition metal oxide clusters. This concerns not only the ground state structure, but also all lowest-energy isomers within a thermally accessible energy range. Identification of these states requires proper sampling of the vast configurational space, suitably carried out by Monte Carlo (MC) based schemes. In order to make such simulations quantitative, they have to be based on reliable first-principles energetics, e.g. from density-functional theory. Due to the high computational cost of the latter techniques, utmost efficiency of the MC algorithms in terms of energy and force calls is mandatory.
As a prelude to targeted first-principles MC simulations, we therefore assess and optimize the efficiency of different MC schemes like basin hopping [1] or Wang-Landau sampling [2]. As representative test systems we use M3O, M5O3 and M7O7 (M = Ru, Pd) oxide clusters described by a model Lennard-Jones potential. Since the evaluation of forces in first-principles methods is computationally more expensive than the calculation of energies, special emphasis is put on minimizing the number of required structural relaxations in the MC algorithms.
[1] D. Wales et al., Science 285, 1368 (1999).
[2] M. Scott Shell et al., Phys. Rev. E 66, 056703 (2002).